Biofuel is generally a fuel derived from biomass, i.e., recently living organisms or their metabolic byproducts, such as manure from animals. Biofuel is desirable because it is a renewable energy source, unlike other natural resources such as petroleum, coal and nuclear fuels. Biofuel includes, inter alia, biologically produced alcohols, such as methanol, ethanol, propanol and butanol. Generally, such biologically produced alcohols can be formed by the action of microbes and enzymes through fermentation of biomass. For example, methanol can be produced from fermentation of wood or other organic materials or formed naturally in the anaerobic metabolism of many varieties of bacteria. Similarly, ethanol can be mass-produced by fermentation of starch or sugar which can be found in a wide variety of crops such as sugar cane, sugar beet and corn. Furthermore, butanol and ethanol can be produced from starch using Clostridium acetobutylicum, a commercially available bacterium, in the A.B.E. (Acetone, Butanol, Ethanol) process. The A.B.E. process was an industry standard before the late 1940's when oil started to become the dominant energy source for its low cost.
Recently, because of concerns over global warming, rising oil prices as well as decreasing oil reserves and increasing political instability in oil producing countries around the world, there are renewed interests from governments, industries and academics in biofuels, particularly biologically produced alcohols. However, methanol, ethanol and propanol are volatile enough that they can cause engine vapor lock and evaporative emission problems. Furthermore, methanol, ethanol and propanol have a high affinity to water and therefore, they generally contain an undesirable amount of water that can cause corrosive problem to internal combustion engines that use them as fuels.
Butanol may be more suited as a biofuel than methanol, ethanol and propanol because the former is less volatile and more hydrophoblic than the latter. However, it is unclear whether the current butanol production methods are economically viable. As a result, there is a need for biofuels that can be produced economically. Further, there is also a need for biofuels that have a low affinity toward water. Further, there is also a need for biofuels that can be made reliably and reproducibly for use in internal combustion engines such as gasoline engines.